The present application relates to semiconductor device fabrication, and more particularly, to a method of recessing a cobalt gate or contact or interconnect metal for enabling implementation of self-aligned gate or contacts.
Transistors, such as field effect transistors (FETs) are the basic elements of microelectronics and integrated circuits. There has been a continuous drive to scale down or shrink transistors and other semiconductor devices to increase density and improve processing performance. One technique that is used to fabricate transistors is known as a replacement metal gate (RMG) process. A replacement metal gate process involves creating a sacrificial gate during fabrication, and then later replacing the sacrificial gate with a metal gate electrode.
Continuing scaling in manufacturing of complementary-metal-oxide-semiconductor (CMOS) transistors has recently lead to the development of self-aligned contacts, which are used to contact the source and drain (S/D) of the FETs. In order to form self-aligned contacts with current RMG integration schemes, the metal gate electrode needs to be recessed such that a dielectric gate cap can be formed on top of the recessed metal gate electrode to isolate the gate from the S/D contacts. The dielectric gate cap prevents potential shorting between the gate and the S/D contact.
Cobalt (Co) is a promising conductive material used as a metal gate electrode and contact metal due to its low resistance. However, Co cannot be recessed using a dry etch process that is commonly employed in recessing conventional gate metals such as tungsten (W) and aluminum (Al). Therefore, there remains a need for providing a method that allows recessing of a Co gate metal and contact metal for enabling implementation of self-aligned gates or contacts.